Effect of Silver Addition on Transient and Steady State Creep Characteristics of Eutectic Sn-9Zn Binary Alloy

Transient, and steady state creep characteristics of Sn-9Zn lead-free solders and Sn-9Zn-2Ag ternary alloy was investigated in the temperature range from 323 to 403 K near the transformation temperatures at different five stresses ranged from 3.62 to 11.22 MPa. Both alloys showed improvement in the creep parameters n and β. The value of n and β are higher in ternary than in binary. The activation energies of transient creep of Sn-9Zn binary and Sn-9Zn-2Ag ternary alloy have been found to be 20.16:28.82 kJ/mole and 14.01:20.22 kJ/mole, in low and high temperature range. The relationship through steady-state creep rate ε´st and the stress ϭ is ε´st =Cϭm wherever m=(∂lnε´st/∂lnϭ), is the strain rate sensitivity parameter. This exponent is raised with rising T and ϭ in both alloys. The activation energies of steady creep of Sn-9Zn binary and Sn-9Zn-2Ag ternary alloy have been found to be 21.99:24.73 kJ/mole and 15.13:22.07 kJ/mole, in low and high temperature zones respectively. Addition of small amount of Ag (2%) to the binary alloy raised its creep behaviour and ductility and was found to be enhancing the plasticity of the ternary alloys. This behaviour was attributed to the formation of inter metallic compounds (IMCs) Ag3Sn during solidification. Micro-structural variations were studied by Optical microscope (OM), and X-ray diffraction.